Balloon catheters and systems and methods for delivering stents using such catheters

ABSTRACT

Apparatus and methods are provided for treating lesions within a blood vessel include a two-layer angioplasty balloon designed for the simultaneous deployment of multiple balloon-expanded stents. The high-compliance (elastic) outer balloon secures stent position. The low-compliance (inelastic) inner balloon drives angioplasty and stent expansion. Stent deployment starts with the injection of a small quantity of fluid into the outer balloon, which bulges slightly at both ends and into the spaces between the stents and, once the stent has expanded a little, between the struts of the stents. The injection port to the outer balloon is then closed, and fluid is injected only into the inner balloon, which expands, opening the stents.

RELATED APPLICATION DATA

This application is a continuation of co-pending application Ser. No.14/133,542, filed Dec. 18, 2013, and issuing as U.S. Pat. No. 9,486,347,the entire disclosure of which is expressly incorporated by referenceherein.

FIELD OF THE INVENTION

The present invention relates generally to apparatus and methods fortreating stenoses, occlusions, or other lesions within a body lumen,such as an artery or other blood vessel, and, more particularly, toballoon catheters for delivering stents, and to systems and methods fortreating lesions within body lumens.

BACKGROUND

Tubular endoprosthesis or “stents” have been suggested for dilating orotherwise treating stenoses, occlusions, and/or other lesions within apatient's vasculature or other body lumens. For example, aself-expanding stent may be maintained on a catheter in a contractedcondition, e.g., by an overlying sheath or other constraint, anddelivered into a target location, e.g., a stenosis within a blood vesselor other body lumen. When the stent is positioned at the targetlocation, the constraint may be removed, whereupon the stent mayautomatically expand to dilate or otherwise line the vessel at thetarget location.

Alternatively, a balloon-expandable stent may be carried on a catheter,e.g., crimped or otherwise secured over a balloon, in a contractedcondition. When the stent is positioned at the target location, theballoon may be inflated to expand the stent and dilate the vessel.

Balloon-expanded stents tend to be relatively stiff and straight, as arethe balloons used to deliver them, which reduces the ability of thestents to conform to the shape of vessels that are curved and/orangulated. Curved connectors between rings of certain stent designs mayallow bending of the unexpanded stent, but such connectors rarelyprovide enough differential lengthening to allow significant bending ofthe expanded stent because the connectors are made from the sameinelastic material used throughout the stent. Moreover, if such a fullyexpanded stent were capable of bending easily, e.g., to accommodate abend in the artery, the stent may be capable of bending repeatedly inresponse to arterial motion, increasing risk of the stent becomingwork-hardened and/or breaking, e.g., after deployment within a bodylumen, such as a cardiac vessel, within which the stent may experiencesignificant dynamic forces. The interface between the end of asubstantially stiff, straight balloon-expanded stent and a relativelysoft, otherwise curved artery may also become the focus of stress. Theresulting micro-trauma may cause inflammation, scarring, and/orflow-limiting narrowing, especially when the artery stretches or bendsrepeatedly with the cardiac cycle, respiratory excursion, and/orflexion/extension of a joint.

One solution involves the implantation of many short unconnected stents,so that the stented artery can bend, just as a long train bends. Thesimultaneous delivery of multiple short balloon-expanded stents iscomplicated by the tendency of individual stents to migrate relative tothe balloon during inflation. When a conventional balloon on a ballooncatheter is expanded, one end of the balloon may initially expand beforethe other, which may cause the stent to migrate away from the initiallyexpanding end and/or compress the stent axially, or both ends may expandinitially before a central region carrying the stent, which may causethe stent to compress or otherwise deform undesirably. If this occurs,the actual position of the stent may be difficult to control, whichrisks the stent being deployed misaligned relative to a desiredlocation. This aspect of balloon expansion may be particularlyproblematic when deploying many short stents.

Accordingly, an improved apparatus and methods for delivering stentswould be useful.

SUMMARY OF THE INVENTION

The present invention is directed to apparatus and methods for treatingstenoses, occlusions, or other lesions within a body lumen, such as anartery or other blood vessel. More particularly, the present inventionis directed to apparatus and methods for delivering and expanding stentswithin a body lumen. The apparatus, systems, and methods describedherein may involve simultaneous delivery of multiple stents and/ormaintaining multiple stents in substantially stable positions relativeto one another and a balloon over which the stents are mounted.

One solution described herein is to substitute a series of relativelyshort, independent stents for a single, relatively long stent. In thisapproach, the stents may function similar to cartilage rings of thetrachea or the hoops of a dryer hose, e.g., maintaining luminal supportwithout greatly reducing the flexibility of the overall stent/arterycomposite. Despite providing interrupted support, short stents maysatisfy the patency requirements of a post-angioplasty artery, which mayotherwise be prone to dissection and luminal compression from dilatationresistant plaque.

Most dissections spiral down the affected artery, and are connected tothe main lumen by only one or two transverse tears in the intima. Ashort stent near the tear may be sufficient to interrupt flow throughthe entire dissection, and a series of short stents may interrupt anytendency of localized dissections to propagate down the artery. A seriesof short stents may also be equally effective at dealing with the usualrigid atherosclerotic plaque, which, like a tabletop, does not needcontinuous support throughout its length.

Balloon-expanded stents may have advantages over self-expanding stents,especially when multiple, relatively short stents are being delivered. Ashort balloon-expanded stent may be carried on the outer surface of theballoon to the arterial wall, which may aid in maintaining control overposition and orientation of the stent(s) throughout delivery anddeployment. The same is not true of a relatively short self-expandingstent, which may tend to jump and twist in the interval between releasefrom a delivery sheath and/or other deployment within an artery.

Current balloon-expanded stents tend to suffer from the same problem:the stent and balloon cannot be attached securely to one another becausethey expand in different ways. The stents generally stretch, while thenon-compliant balloons typically used to deliver them unfurl. Compliantballoons, on the other hand, are capable of stretching, just like astent, but cannot withstand the pressures typically used for arterialdilatation and stent expansion.

The lack of a stable connection between the balloon and theballoon-expanded stent is compounded by a phenomenon called“dog-boning,” in which a non-compliant balloon opens first at the endswhere there is no stent to impede expansion. Expansion at the ends maycontinue until they reach full diameter, whereupon expansion mayprogress from the ends towards the middle of the balloon. Multiple,short stents may be pushed down the resulting sloped surface of theballoon towards the middle of the balloon, where they may collide andexpand, without the intended spacing. The apparatus and methodsdescribed herein may substantially maintain desired spacing of multiplespaced-apart stents during delivery and/or expansion.

For example, in one aspect, the apparatus and methods herein combine thepressure tolerance of an internal low-compliance (high-pressure) balloonwith the elasticity of an external high-compliance (low-pressure)balloon. Optionally, saline or other fluids and/or lubricious (e.g.,hydrogel) coatings between the two balloons, may facilitate the balloonssliding relative to one another, and/or may facilitate the outer balloonconforming to irregularities on the inner surface of the stent(s)delivered by the balloons, which may ensure that the two stay togetherthroughout expansion.

In accordance with one embodiment, a system is provided for treating abody lumen that includes an elongate tubular member including a proximalend, a distal end sized for introduction into a body lumen, and a firstinflation lumen extending between the proximal and distal ends; an innerballoon on the distal end formed from substantially inelastic materialdefining a central region, the inner balloon expandable from a deliveryconfiguration in which the inner balloon is rolled or folded around thedistal end, and an enlarged configuration in which the central regiondefines a substantially uniform diameter when inflation media isintroduced into the first inflation lumen; and an outer balloon on thedistal end overlying the inner balloon, the outer balloon formed fromelastic material such that the outer balloon expands elastically whenthe inner balloon is expanded from the contracted configuration to theenlarged configuration.

Optionally, at least one of the inner and outer balloons include one ormore features to prevent substantial transfer of non-radial forcesgenerated, when the inner balloon expands from the contractedconfiguration to the enlarged configuration, to be transferred to theouter balloon. In exemplary embodiments, the one or more features mayinclude one or more of lubricious fluid disposed within a space betweenthe inner and outer balloons, a lubricious outer surface of the innerballoon, a lubricious inner surface of the outer balloon, e.g., byapplying a lubricious coating to one or both surfaces and/or forming oneor both balloons from lubricious material, and the like.

A single stent may be disposed around the outer balloon over at least aportion of the central region of the inner balloon, or a plurality ofstents may be disposed around the outer balloon and spaced apart fromone another and aligned over the central region of the inner balloon.Optionally, the outer balloon may include one or more features on theouter surface thereof that engage the stent(s) to prevent migration ofthe stent(s) relative to the outer balloon.

In accordance with another embodiment, an apparatus for treating a bodylumen is provided that includes an elongate tubular member including aproximal end, a distal end sized for introduction into a body lumen, anda first inflation lumen extending between the proximal and distal ends;an inner balloon on the distal end and including first and second endsattached to the distal end, the inner balloon formed from substantiallyinelastic material and having an interior communicating with the firstinflation lumen such that a central region of the inner balloon expandsto a substantially uniform diameter when inflation media is introducedinto the first inflation lumen; an outer balloon on the distal endoverlying the inner balloon, the outer balloon formed from elasticmaterial, at least one of an inner surface of the outer balloon and anouter surface of the inner balloon comprising lubricious material suchthat the outer surface slidably engages the inner surface when the innerballoon is expanded; and a plurality of stents disposed around the outerballoon and spaced apart from one another and aligned over the centralportion of the inner balloon.

In accordance with still another embodiment, an apparatus for treating abody lumen is provided that includes an elongate tubular memberincluding a proximal end, a distal end sized for introduction into abody lumen, and first and second inflation lumens extending between theproximal and distal ends; an inner balloon on the distal end andincluding first and second ends attached to the distal end, the innerballoon formed from substantially inelastic material and having aninterior communicating with the first inflation lumen such that acentral region of the inner balloon expands to a substantially uniformdiameter when inflation media is introduced into the first inflationlumen; an outer balloon on the distal end overlying the inner balloon,the outer balloon formed from elastic material and having an interiorcommunicating with the second inflation lumen for expanding the outerballoon independently of expansion of the inner balloon; and a pluralityof stents disposed around the outer balloon and spaced apart from oneanother and aligned over the central region of the inner balloon.

In accordance with another embodiment, a method is provided for treatinga lesion within a body lumen that includes providing a delivery catheterincluding inner and outer balloons on a distal end thereof, the innerballoon in a delivery configuration in which a central region of theinner balloon is rolled or folded around the distal end, and one or morestents mounted on the outer balloon over the central region of the innerballoon. The distal end may be introduced into a body lumen within thepatient's body, and the inner balloon may be expanded to an enlargedconfiguration in which the inner balloon at least partially unrolls orunfolds, thereby radially expanding the outer balloon and the one ormore stents thereon, wherein an interface between the inner and outerballoons prevents non-radial forces generated by the inner balloon as itunrolls or unfolds from being transferred to the one or more stents asthey are expanded.

In accordance with yet another embodiment, a method for treating apatient is provided that includes providing a delivery catheterincluding inner and outer balloons on a distal end thereof, and aplurality of stents spaced apart from one another over central regionsof the inner and outer balloons; introducing the distal end into a bodylumen within the patient's body with the inner and outer balloons in acontracted condition; inflating the outer balloon to engage the stentswithout expanding the stents; and expanding the inner balloon tosubstantially simultaneously expand the stents and the outer balloonaround the inner balloon, the inner balloon sliding relative to theouter balloon such that the outer balloon engages the stents to preventsubstantial migration of the stents as the inner balloon expands.

Other aspects and features of the present invention will become apparentfrom consideration of the following description taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is best understood from the following detailed descriptionwhen read in conjunction with the accompanying drawings. It will beappreciated that the exemplary apparatus shown in the drawings are notnecessarily drawn to scale, with emphasis instead being placed onillustrating the various aspects and features of the illustratedembodiments.

FIG. 1 is a perspective view of an exemplary embodiment of a ballooncatheter carrying a plurality of independent stents.

FIG. 2 is a longitudinal cross-sectional view of a distal portion of theballoon catheter of FIG. 1 taken along line 2-2 in FIG. 1.

FIG. 3 is a cross-sectional view of the distal portion of the ballooncatheter of FIG. 1 taken along line 3-3 in FIG. 2 with the balloons andstents in contracted or delivery conditions.

FIG. 4 is a cross-sectional view of the distal portion of the ballooncatheter shown in FIG. 3 after partially expanding the balloons andstents.

FIG. 5 is a perspective view of an exemplary embodiment of a balloonthat may be provided as an inner balloon on the balloon catheter of FIG.1.

FIG. 6 is a detail of the balloon of FIG. 5 being folded about itsperiphery.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Turning to the drawings, FIGS. 1-3 show an exemplary embodiment of anapparatus 10 including a balloon catheter 18 and one or more stents 50thereon, e.g., for delivering the stent(s) 50 into a body lumen and/orotherwise treating a lesion therein (not shown). As shown in FIG. 2,seven (7) spaced-apart independent stents 50 are shown carried on theballoon catheter 18, although it will be appreciated that any desirednumber of stents 50 may be provided, such as two, three, four, five,six, or more stents (not shown), as desired. Optionally, the apparatus10 may be provided as part of a kit or system including one or moreadditional components, such as one or more syringes or other sources ofinflation media, a guide catheter (not shown), and/or one or moreguidewires (one guidewire 90 shown in FIG. 2).

Generally, as best seen in FIG. 1, the catheter 18 includes an elongatetubular member 20 having a proximal end 22, a distal end 24 sized forintroduction into a patient's body, and one or more lumens 26 (best seenin FIG. 2) extending between the proximal and distal ends 22, 24,thereby defining a longitudinal axis 28 extending between the proximaland distal ends 22, 24. As shown, the catheter 18 may include a pair ofconcentric and/or overlapping balloons or other expandable members 30 onthe distal end 24, e.g., a first or inner balloon 30 a and a second orouter balloon 30 b, for expanding the plurality of stents 50 carriedthereon, as described further below. Optionally, the distal end 24and/or the balloon(s) 30 may include one or more markers, e.g., one ormore bands of radiopaque material (not shown), to facilitate positioningthe catheter 18 within a patient's body, also as described furtherelsewhere herein.

The catheter 18 may be formed from one or more tubular bodies, e.g.,having variable flexibility along its length, if desired. For example,the distal end 24 may be substantially flexible to facilitateintroduction through tortuous anatomy, e.g., terminating in a rounded,tapered, and/or other substantially atraumatic distal tip 25. Theproximal end 22 may be substantially flexible, semi-rigid, or rigid,e.g., having sufficient column strength to facilitate advancing thedistal end 24 through a patient's vasculature by pushing on and/orotherwise manipulated the proximal end 22. The catheter 18 may be formedfrom plastic, metal, or composite materials, e.g., a plastic materialhaving one or more wires, braids, or other reinforcement elements (notshown) embedded or otherwise provided within the wall of the catheter18, which may prevent kinking and/or buckling of the catheter 18 duringadvancement or other manipulation.

As shown in FIG. 1, the catheter 18 may include a handle 40 on theproximal end 22, e.g., to facilitate manipulating the catheter 18. Thehandle 40 may include one or more ports 42 communicating with respectivelumens 26 within the catheter 18, as described further below. The handle40 may be molded, machined, or otherwise formed from plastic, metal, orcomposite material, e.g., providing an outer casing, which may becontoured or otherwise shaped to ease manipulation. The proximal end 22of the catheter 18 may be attached to the handle 40, e.g., by bonding,cooperating connectors, interference fit, and the like.

In the exemplary embodiment shown in FIG. 2, the catheter 18 includes atleast three lumens 26 extending between the proximal and distal ends 14,16. For example, the catheter 18 may include inflation lumens 26 a, 26 bthat extend from respective side ports 42 a, 42 b on the handle 40through the catheter 18 to openings 27 a, 27 b that communicate withinteriors 36 a, 36 b of respective balloons 30 a, 30 b. Alternatively,the second inflation lumen 26 b and second side port 42 b may beomitted, e.g., if the outer balloon 30 b is not inflated independent ofthe inner balloon 30 a, as described elsewhere herein. The side ports 42a, 42 b on the handle 40 may include one or more connectors, e.g., aluer lock connector (not shown), one or more seals (also not shown), andthe like. A source of inflation media and/or vacuum, e.g., a syringefilled with saline or other inflation media (not shown), may beconnected to the side ports 42 a, 42 b, e.g., directly or via tubing(also not shown), for expanding and/or collapsing the balloons 30independently of one another.

In addition, the catheter 18 may include an instrument lumen 26 c thatextends from port 42 c on the handle 40 to an opening 27 c in the distaltip 25. The instrument lumen 26 c may have sufficient size to allow aguidewire or other rail or instrument (e.g., guidewire 90 shown in FIG.2) to be inserted therethrough, e.g., to facilitate introducing thecatheter 18 into a patient's body, as described further below. The port42 c may include one or more seals (not shown) in or adjacent the port42 c that prevent fluid, e.g., blood, from flowing proximally out of theport 42 c, yet allow one or more instruments to be inserted therethroughand into the instrument lumen 26 c. Alternatively, a “rapid exchange”instrument lumen may be provided that extends from the opening 27 c to aproximal port (not shown) proximal to and/or closer to the balloons 30than the handle 40.

As shown in FIG. 2, the lumens 26 may be concentric with one another,e.g., with inner lumen 26 a communicating with the interior 36 a of theinner balloon 30 a and outer lumen 26 b communicating with the interior36 b of the outer balloon 30 b. Alternatively, the lumens 26 may bedisposed in side-by-side and/or other arrangements (not shown) withinthe body of the catheter 18. In an alternative embodiment, the outerlumen 26 b may be omitted, e.g., if the outer balloon 30 b is notindependently expandable, as described further elsewhere herein.

Returning to FIGS. 1 and 2, in the embodiment shown, the first or innerballoon 30 a and second or outer balloon 30 b on the distal end 24 areexpandable independently of one another. For example, the ends 32, 34 ofthe balloons 30 may be bonded or otherwise secured to the distal end 24of the catheter 18, e.g., by bonding with adhesive, sonic welding, usingan annular collar or sleeve (not shown), and the like. The rest of theballoons 30 including central or main regions 38 remain substantiallyfree and/or expandable relative to one another and the distal end 24.

As best seen in FIG. 2, the inner balloon 30 a may include a proximalend 32 a attached directly to the distal end 24 of the catheter 18 and adistal end 34 a attached directly to the distal end 24 proximal toinstrument lumen port 27 c and/or otherwise adjacent the distal tip 25.The outer balloon 30 b includes a first or proximal end 32 b thatextends at least partially over the proximal end 32 a of the innerballoon 30 a and a second or distal end 34 b. For example, the proximalend 32 b may be attached to the distal end 24 of the catheter body 20proximal to the proximal end 32 a of the inner balloon 30 a and/or overthe proximal end 32 a itself. The distal end 34 b of the outer balloon30 b may be attached over or adjacent to the distal end 34 a of theinner balloon 30 a, e.g., by bonding, sonic welding, using an annularcollar or sleeve (not shown), and the like, as described elsewhereherein.

The inner balloon 30 a may be expandable from a contracted or deliverycondition (shown in FIG. 3) to an enlarged or dilation condition (shownin FIG. 4). In an exemplary embodiment, shown in FIG. 5, the innerballoon 30 a may be shaped such that the central or main region 38 aexpands to a substantially uniform cylindrical shape in the enlargedcondition, e.g., having a diameter between about two and ninemillimeters (2-9 mm) when fully expanded, and a length between about tenand two hundred millimeters (10-200 mm). The inner balloon 30 a may beat least partially rolled or folded, e.g., to define a plurality offolds 39 in the contracted condition, as shown in FIG. 6, e.g., tominimize a profile of the inner balloon 30 a. On either side of thecentral region 38 a, the inner balloon 30 a may transition to theproximal and distal ends 32 a, 34 a. The proximal and distal transitionportions 35 a may have a frustoconical or other tapered shape, as shown,or may be substantially blunt (not shown).

For example, the inner balloon 30 a may be formed from substantiallyinelastic or non-compliant material, e.g., PET, nylon, or mid to highdurometer PEBAX, such that the inner balloon 30 a expands to apredetermined size in its enlarged condition once sufficient fluid isintroduced into the interior 36 a of the balloon 30 a. Thus, the innerballoon 30 a may be expanded to a relatively high pressure, e.g.,between about eight and twenty atmospheres (8-20 ATM), withoutsubstantial risk of rupturing, e.g., to apply sufficient pressure toexpand and/or dilate the stent(s) 50 and/or dilate a lesion within whichthe balloons 30 are expanded, as described further below.

Similarly, the outer balloon 30 b may also be expandable from acontracted condition (also shown in FIG. 3) to an enlarged condition(shown in FIG. 4). Unlike the inner balloon 30 a, the outer balloon 30 bmay be formed from substantially elastic and/or compliant material,e.g., silicone, polyurethane, polyethylene, or low to mid durometerPEBAX, such that the outer balloon 30 b may stretch as it is expanded toa variety of sizes, e.g., depending upon the volume and/or pressure offluid within the interior 36 b. Optionally, the outer balloon 30 b mayhave a relaxed size smaller than the inner balloon 30 a in itscontracted condition, e.g., such that the outer balloon 30 b ispartially stretched over the inner balloon 30 a when the outer balloon30 b is mounted on the distal end 24 of the catheter 18. Thus, the outerballoon 30 b may initially be under some tension, which may helpmaintain the inner balloon 30 a in the contracted condition, e.g., toprevent substantially unintended movement of the folds 39.Alternatively, the outer balloon 30 b may have a relaxed size similar toor slightly larger than the inner balloon 30 a in the contractedcondition.

The outer balloon 30 b may have a substantially uniform wall thickness,e.g., between the proximal and distal ends 32 b, 34 b. Alternatively,the wall thickness may vary, e.g., to provide one or more features onthe central region 38 b for engaging the stent(s) 50 carried thereon, asdescribed elsewhere herein. For example, the outer balloon 30 b mayinclude relatively thin-walled regions, e.g., annular regions 37, spacedapart from one another such that the thin-walled regions 37 are disposedbetween the stents 50 loaded onto the outer balloon 30 b. Thus, thestents 50 may be loaded onto relatively thick-walled regions of theouter balloon 30 b, which may have greater resistance to stretching orotherwise expanding than the thin-walled regions 37.

In addition or alternatively, the outer balloon 30 b may include aplurality of protrusions or indentations configured to substantiallysecure the stents 50 and/or substantially maintain the spacing of thestents 50, e.g., during introduction into a target body lumen and/orduring expansion of the balloon(s) 30. For example, the outer balloon 30b may include a plurality of protrusions (not shown) sized to bereceived within openings in the stents 50, e.g., annular arrangements ofprotrusions spaced apart from one another corresponding to the desiredspacing of the stents 50 loaded onto the outer balloon. Thus, theprotrusions may be received within respective openings in the stents 50,which may remain engaged together during expansion of the outer balloon30 b, e.g., due to the outer balloon 40 b stretching as the outerballoon 40 b and stents 50 are expanded by the inner balloon 30 a, asdescribed further elsewhere herein.

In addition or alternatively, the outer balloon 30 b may include one ormore features thereon for enhancing traction, friction, and/or otherengagement with structures contacted by the outer balloon 30 b whenexpanded. For example, the outer surface may be treated or textured, mayinclude ribs or other protrusions, and the like (not shown) to increasefriction or other engagement upon expansion.

Optionally, the inner and/or outer balloons 30 a, 30 b may include oneor more features to facilitate slidable engagement or other movement ofthe balloons 30 relative to one another, e.g., during expansion. Forexample, an outer surface 39 a of the inner balloon 30 a and/or an innersurface 39 b of the outer balloon 30 b may include a lubricious coatingor material, e.g., silicone, a hydrophilic material, and the like. Inaddition or alternatively, lubricious fluid, e.g., saline, silicone, andthe like, may be provided within the space between the balloons 30. Forexample, a desired volume of lubricious fluid may be introduced into theinterior 36 b of the outer balloon 30 b at any time before expanding theinner balloon 30 a, e.g., via the second inflation lumen 26 b.Alternatively, if the second inflation lumen 26 b is eliminated, a fixedvolume of lubricious fluid may be disposed within the interior 36 b ofthe outer balloon 30 b, e.g., during manufacturing, to enhance alubricious interface between the inner and outer balloons 30 a, 30 b.

Such materials may allow the inner balloon 30 a to unfold and/orotherwise expand without applying substantial torsional or othercircumferential and/or axial forces to the outer balloon 30 b andconsequently to the stents 50. Thus, as the inner balloon 30 a isinflated, the inner balloon 30 a may apply radially outward forcesagainst the outer balloon 30 b as it expands, and consequently thestents 50, to expand the stents 50 without the outer balloon 30 btransmitting non-radial forces from the inner balloon 30 a to the stents50, which may reduce the risk of migration or other unwanted movement ofthe stents 50.

Returning to FIGS. 1 and 2, the stents 50 may include a plurality ofrelatively short cylindrical or tubular rings that are each expandablefrom a compressed or contracted condition to an expanded condition.Although not shown, each stent 50 may include a plurality of strutsconfigured to facilitate each stent 50 expanding, e.g., including one ormore zigzag pattern of cylindrical cells (not shown). However, unlikeconventional stents, each stent 50 may be relatively short, e.g., havinga length between about two and twelve millimeters (2-12 mm), and only afew cells, e.g., one, two, or three cylindrical cells. In addition, eachstent 50 may be decoupled or independent from the other stents 50, e.g.,such that, although the stents 50 may be expanded substantiallysimultaneously, the expansion of a first stent 50 does not impactexpansion of the other stents 50, and the stents 50 may remain decoupledand/or independent from one another after delivery. Alternatively, theapparatus 10 and systems herein may also be used to deliver a single,e.g., relatively long, stent (not shown) instead of a plurality ofrelatively short stents 50.

The stents 50 may be formed from plastically deformable materialscapable of plastically deforming without failure within a desired rangeof expansion, e.g., allowing the stents 50 to expand about two to eight(2-8) times between the contracted condition and the expanded condition,e.g., from an initial diameter between about one and four millimeters(1-4 mm) to an expanded diameter between about two and twelvemillimeters (2-12 mm).

Optionally, each stent 50 may include features to enhance expansion ofthe stent 50 in a desired manner. For example, one or both ends of eachstent 50 may include cells, struts, and/or other features configured toflare outwardly relative to a central section of the stent 50. Such aconfiguration may accommodate expansion of the intermediate regions 37of the outer balloon 30 b relative to the stents 50, as describedfurther below.

If desired, the stents 50 may include one or more additional features,e.g., one or more radiopaque or other markers, e.g., on each stent 50 oronly on desired stents 50, e.g., the first and last stent on theballoons 30, which may facilitate positioning the stents 50 relative toa target treatment site.

During use, the apparatus 10 may be used to treat a body lumen within apatient's body, e.g., an occlusion, stenosis, or other lesion within anartery or other blood vessel. For example, the lesion may includeatherosclerotic plaque or other material that partially or completelyoccludes blood or other fluid flow within the body lumen, and theapparatus 10 may be used to deliver a plurality of stents 50 to dilateand/or otherwise support the body lumen. In addition, the apparatus 10may facilitate treatment of difficult-to-treat locations, e.g., curved,angulated, and/or tortuous locations within blood vessels, locationsthat move dynamically, e.g., cardiac vessels that may move repeatedlybased on the phases of the cardiac cycle.

Initially, a guidewire (such as the guidewire 90 shown in FIG. 2) orother rail may be introduced into the patient's body until a distal endof the guidewire is disposed within a target location, e.g., across thelesion within a body lumen being treated. For example, a percutaneouspuncture or cut-down may be created at a peripheral location (notshown), such as a femoral artery, carotid artery, or other entry site,and the guidewire may be advanced through the patient's vasculature fromthe entry site, e.g., alone or with the aid of a guide catheter (notshown) to the target location. The guide catheter may be used to advanceone or more instruments (such as any of the catheters or other devicesdescribed herein) over the guidewire and into the target location.

If a lesion completely occludes a body lumen, the guidewire may bedirected through the occlusion, or other devices (not shown) may beadvanced over the guidewire or otherwise in conjunction with theguidewire to create a passage through the lesion for the guidewire.After the guidewire is directed into the body lumen, it may be desirableto at least partially dilate the lesion.

For example, an angioplasty catheter (not shown) may be advanced throughthe guide catheter and/or over the guidewire into and through thelesion, whereupon a balloon or other element on the catheter may beexpanded to at least partially dilate the lesion. If desired, otherprocedures may also be performed at the lesion, e.g., to soften, remove,or otherwise treat plaque or other material forming the lesion, beforethe stents 50 are delivered. After completing any such procedures, anyinstruments advanced over the guidewire may be removed.

To deliver the stents 50 (or a single stent, not shown), a deliverycatheter, such as the catheter 10 shown in FIGS. 1-4 may be used withthe balloons 30 and stents 50 initially in contracted conditions, e.g.,as shown in FIG. 3. For example, with the balloons 30 in the deflated,contracted conditions, the distal end 24 of the catheter 10 may beadvanced over the guidewire 90 (shown in FIG. 2) and/or through a guidecatheter (not shown) from the entry site into a target body lumen. Thecatheter 10 may be positioned such that the distal end 24 extends intoand through the lesion, e.g., until the balloons 30 and stents 50 arecentered or otherwise positioned as desired within the lesion.

The stents 50 may then be expanded and/or otherwise deployed from thecatheter 10, e.g., to place the stents 50 across the lesion, e.g.,spaced apart from one another within the body lumen within and on eitherside of the lesion.

Optionally, to facilitate positioning, the stents 50 and/or balloons 30may be monitored using fluoroscopy or other external imaging, e.g., toobserve and monitor markers (not shown) on the distal end 24, one orboth balloons 30, and/or on the stents 50. For example, markers may belocated on the distal end 24 to identify the ends of the substantiallyuniform main region 38 a of the inner balloon 30 a, and consequently thelocation of the stents 50 carried thereon.

With reference to FIGS. 2-4, the balloons 30 may be inflated orotherwise expanded to expand the stents 50 and/or dilate the body lumen.In an exemplary method, an initial expansion step may involveintroducing inflation media through the second inflation lumen 26 b intothe interior 36 b of the outer balloon 30 b, e.g., to engage the outerballoon 30 b and the stents 50 without substantially expanding thestents 50. For example, as shown in FIG. 2, the outer balloon 30 b maybe inflated to cause the regions 37 between adjacent stents 50 and/orproximal and distal to the first and last stents 50, respectively, tobulge or otherwise expand slightly. The resulting expanded regions 37may substantially secure the stents 50 relative to one another, e.g.,resisting subsequent axial movement of the stents 50.

Next, the inner balloon 30 a may be inflated, e.g., causing the centralregion 38 a to unfold and/or otherwise expand within the outer balloon30 b. As the inner balloon 30 a expands, it may apply a radially outwardforce against the outer balloon 30 b and, consequently, the stents 50.Thus, the stents 50, while remaining substantially independent from oneanother, may be expanded substantially simultaneously with the outerballoon 30 b reducing the risk of the stents 50 migrating.

Due to the ability of the inner balloon 30 a to slide relative to theouter balloon 30 b, e.g., which may be enhanced by one or more coatingsand/or fluid between the balloons 30, any torsional, circumferential,axial forces, and/or other non-radial forces generated by expansion ofthe inner balloon 30 a are not transferred to the stents 50, which mayotherwise cause the stents 50 to shift, slide, twist, and/or otherwisemove other than expanding radially to the expanded condition.

Thus, the inner and outer balloons 30 a, 30 b may have different modesof expansion: the non-compliant inner balloon 30 a may unfold, unroll,or otherwise unfurl, while the compliant outer balloon 30 b stretches.The outer surface 39 of the non-compliant inner balloon 30 a may slidealong the inner surface 39 b of the outer balloon 30 b, e.g., withlittle or no twisting or other non-radial movement transferred from theinner balloon 30 a to the outer balloon 30 b. The outer balloon 30 b, onthe other hand, expands in a substantially similar manner to the stents50, i.e., in the radial direction. Because the outer balloon 30 b andthe stents 50 move together, they may remain in close appositionthroughout deployment. Moreover, at relatively low pressures, thecompliant outer balloon may squeeze its way into the spaces between thestents and/or between individual stent struts. The resulting pattern ofreciprocal engagement may secure the stents 50 in a substantially fixedposition relative to the outer balloon 30 b. Meanwhile, the innerballoon 30 a remains free to slide against the inner surface 39 b of theouter balloon 30 b (e.g., due a lubricious coating and/or fluid betweenthe inner and outer balloons 30 a, 30 b), e.g., to stretch or otherwiseexpand the outer balloon 30 b, and expand the stents 50 without drivingthem on a collision course (e.g., down the slope of a dog-bone from ends32, 34 of the balloons 30 towards the center regions 38). Optionally,given their similar modes of expansion, features (not shown) on theouter surface of the outer balloon 30 b may mate with correspondingfeatures on the stents 50, further minimizing the potential for movementbetween the two, and further securing stent position.

In an alternative embodiment, the outer balloon 30 b may not beexpandable independent of the inner balloon 30 a. For example, thesecond inflation lumen 26 b may be omitted, and the outer balloon 30 bmay be slidable around the inner balloon 30 a. Thus, during inflationand consequent expansion of the inner balloon 30 a, the outer balloon 30b may be stretched and/or otherwise expanded, thereby substantiallysimultaneously expanding the stents 50.

Once the stents 50 are fully expanded and/or deployed, the balloon(s) 30may be deflated and/or otherwise collapsed back to the contractedconditions to facilitate removal of the catheter 10, leaving the stents50 deployed within the target location. For example, inflation media maybe evacuated from the interiors 36 of the balloons 30, e.g.,substantially simultaneously or sequentially, e.g., first deflating theinner balloon 30 a and then deflating the outer balloon 30 b todisengage the outer balloon 30 b from the expanded stents 50 or firstdeflating the outer balloon 30 b and then deflating the inner balloon 30a.

Optionally, each stent 50 may include flarable end regions (not shown),which may be flared when the outer balloon 30 b is initially inflated toengage the stents 50. In this manner, the stents 50 may become seated inannular valleys in the outer balloon 30 b, which may reduce the risk ofaxial migration of the stents 50 relative to one another. Once thestents 50 are expanded and/or engaged with the wall of the body lumen,the outer balloon 30 b may be deflated to disengage the flared ends ofthe stents 50, and the inner balloon 30 may optionally be inflatedfurther to plastically deform the stents 50, e.g., into unflaredsubstantially uniform expanded diameters.

Alternatively, the catheter 18 may be used to deliver a single,relatively long stent (not shown), which may extend along a majority ofthe center region 38 b of the outer balloon 30 b. As with deliveringmultiple stents, decoupling the inner and outer balloons 30 a, 30 b maycause the inner balloon 30 a to apply radial forces to expand and/ordilate the stent, while preventing non-radial forces generated by theinner balloon 30 a during unfurling or other movement to be transferredto the stent, thereby reducing the risk of a single stent being twistedor otherwise moving in an undesirable manner as the inner balloon 30 ais expanded. Such decoupling may also facilitate delivering one or morestents within tortuous anatomy, e.g., such that any undesired forcesgenerated by the inner balloon 30 a during expansion within anon-cylindrical body lumen, e.g., a curved, angulated, or other vessel,may be absorbed by the interface between the inner and outer balloons 30a, 30 b, rather than transferred to the stent(s) being delivered.

In yet another alternative, the outer balloon 30 b may be partiallyinflated before introducing the distal end 24 of the catheter 10 intothe patient's body. In this embodiment, the outer balloon 30 b may beinflated sufficiently to engage the stents 50 (e.g., using protrusionson the outer balloon 30 b, thin-walled regions 37, and/or frictionalsurfaces and/or materials) to prevent substantial migration while thedistal end 24 is introduced into the patient's body and advanced to thetarget location. Once positioned where desired, the inner balloon 30 amay be inflated to expand the stents 50 within the target location,e.g., similar to other embodiments herein.

It will be appreciated that elements or components shown with anyembodiment herein are exemplary for the specific embodiment and may beused on or in combination with other embodiments disclosed herein.

While the invention is susceptible to various modifications, andalternative forms, specific examples thereof have been shown in thedrawings and are herein described in detail. It should be understood,however, that the invention is not to be limited to the particular formsor methods disclosed, but to the contrary, the invention is to cover allmodifications, equivalents and alternatives falling within the scope ofthe appended claims.

I claim:
 1. A method for treating a patient, comprising: providing adelivery catheter including inner and outer balloons on a distal endthereof, the inner balloon in a delivery configuration in which acentral region of the inner balloon is rolled or folded around thedistal end, and one or more stents mounted on the outer balloon over thecentral region of the inner balloon; introducing the distal end into abody lumen within the patient's body; and expanding the inner balloon toan enlarged configuration in which the inner balloon at least partiallyunrolls or unfolds, thereby radially expanding the outer balloon and theone or more stents thereon, wherein an interface between the inner andouter balloons prevents non-radial forces generated by the inner balloonas it unrolls or unfolds from being transferred to the one or morestents as they are expanded.
 2. The method of claim 1, wherein theinterface comprises the inner balloon sliding along an inner surface ofthe outer balloon.
 3. The method of claim 1, further comprisinginflating the outer balloon to engage the one or more stents withoutexpanding the one or more stents before expanding the inner balloon. 4.The method of claim 1, wherein a single stent is carried on the outerballoon.
 5. The method of claim 1, wherein a plurality of stents arecarried on the outer balloon, the plurality of stents spaced apart anddecoupled from one another, and wherein expanding the inner ballooncomprises substantially simultaneously expanded the plurality of stents.6. The method of claim 1, wherein the outer balloon has a low frictioninner surface that slidably engages an outer surface of the innerballoon during expansion of the inner balloon.
 7. The method of claim 1,wherein the inner balloon has a low friction outer surface that slidablyengages an inner surface of the outer balloon during expansion of theinner balloon.
 8. The method of claim 1, wherein the interface comprisesat least one of a lubricious coating on an outer surface of the innerballoon and a lubricious coating on an inner surface of the outerballoon.
 9. The method of claim 1, wherein the interface compriseslubricious fluid disposed within a space between the inner and outerballoons.
 10. A method for treating a patient, comprising: providing adelivery catheter including inner and outer balloons on a distal endthereof, and a plurality of stents spaced apart from one another overcentral regions of the inner and outer balloons; introducing the distalend into a body lumen within the patient's body with the inner and outerballoons in a contracted condition; inflating the outer balloon toengage the stents without expanding the stents; and expanding the innerballoon to substantially simultaneously expand the stents and the outerballoon around the inner balloon, the inner balloon sliding relative tothe outer balloon such that the outer balloon engages the stents toprevent substantial migration of the stents as the inner balloonexpands.
 11. The method of claim 10, wherein the inner balloon is foldedinto the contracted condition, and wherein the inner balloon unfolds asthe inner balloon is expanded, the outer balloon allowing the folds toslide easily within the outer balloon.
 12. The method of claim 10,wherein the outer balloon comprises regions between adjacent stents thatexpand between the stents when the outer balloon is inflated.
 13. Themethod of claim 10, wherein the outer balloon comprises spaced-apartfeatures on the outer surface thereof that engage the plurality ofstents to prevent axial migration of the stents relative to the outerballoon.
 14. The method of claim 13, wherein the spaced-apart featurescomprise protrusions extending outwardly from the outer surface of theouter balloon.
 15. The method of claim 13, wherein the spaced-apartfeatures comprise indentations formed in the outer balloon having shapesconfigured to receive one or more stents therein.
 16. The method ofclaim 8, wherein each of the plurality of stents is uncoupled from oneanother.
 17. The method of claim 8, wherein each of the plurality ofstents is deployable independent of one another.
 18. The method of claim8, wherein each of the plurality stents is formed from plasticallydeformable materials that plastically deform to expand when the innerballoon is expanded from the delivery configuration to the enlargedconfiguration.
 19. An apparatus for treating a body lumen, comprising:an elongate tubular member including a proximal end, a distal end sizedfor introduction into a body lumen, and a first inflation lumenextending between the proximal and distal ends; an inner balloon on thedistal end formed from substantially inelastic material defining acentral region, the inner balloon expandable from a deliveryconfiguration in which the inner balloon is rolled or folded around thedistal end, and an enlarged configuration in which the central regiondefines a substantially uniform diameter when inflation media isintroduced into the first inflation lumen; and an outer balloon on thedistal end overlying the inner balloon, the outer balloon formed fromelastic material such that the outer balloon expands elastically whenthe inner balloon is expanded from the contracted configuration to theenlarged configuration.